紫外波长对UV/Cl_2高级氧化去除水中有机物的影响

Effect of ultraviolet wavelength on organic matter removal from water by UV/Cl_2 advanced oxidation

为明确紫外波长对UV/Cl_2高级氧化体系的影响,使用中心波长分别为267、275和286 nm的发光二极管LED作为光源,探究Cl_2光解动力学、UV/Cl_2体系自由基生成、对模式化合物溶液以及天然水、再生水TOC的去除。结果表明:在中性或酸性体系中,267 nm最接近HClO最大吸收波长237 nm,吸光度和量子产率均较大,羟基自由基产生水平较高,有机物去除效果较好;在碱性体系中,286 nm最接近ClO^-最大吸收波长292 nm,尽管量子产率较小,但吸光度很大,有机物去除效果较好;由于水杨酸在292 nm附近有较强的竞争吸收,使用UV_(286)去除水杨酸效果被削弱。应用UV/Cl_2技术选择波长时需要考虑吸光度、量子产率、竞争吸收等因素;对于弱碱性天然水或再生水,采用波长为292 nm的紫外光一般可获得较优处理效果。

TodeterminetheeffectofultravioletwavelengthontheUV/Cl2 advancedoxidationsystem,Cl2 photolysis kinetics, free radicals generation in UV/Cl2 system, TOC removal from model compound solutions, natural water and reclaimed water, were investigated by using light-emitting diodes(LEDs) as ultraviolet light sources with central wavelengths of 267, 275 and 286 nm, respectively. The results showed that in neutral or acidic systems,267 nm is the closest wavelength to the maximum absorption one of HClO(237 nm), and higher absorbency and quantum yield of chlorine photolysis reaction with UV267 than other two wavelengths occurred, which could lead to more hydroxyl radicals and higher organic matter removal efficiency. In alkaline system, 286 nm is the closest wavelength to the maximum absorption one of ClO-(292 nm), compared with other two wavelengths, the quantum yield of chlorine photolysis reaction with UV286 is lower, while the absorbency is considerably higher, and a higher organic matter removal efficiency was also obtained.In addition,salicylic acid removal by the UV/Cl2 advanced oxidation system with UV286 was weakened due to its strong competitive absorption near 292 nm. It needs to consider absorbance, quantum yield and competitive absorption when the appropriate UV light wavelength is chosed for UV/Cl2 practical application. Generally, good performance of the UV/Cl2 advanced oxidation system on weakly alkaline natural or reclaimed water treatment could be achieved when using 292 nm UV light.